Volatile corrosion inhibitor materials, such as vapor phase corrosion inhibitors, are widely utilized as species impregnated within or otherwise disposed upon various substrates. The volatile corrosion inhibitor (VCI) materials emit vapor phase corrosion inhibitors over time, even at ambient conditions, such that by placing the VCI-containing substrate at a location adjacent to corrosion-susceptible materials, the vapor phase corrosion inhibitors operably act to protect such materials from corrosion.
In some embodiments of the prior art, volatile corrosion inhibitor materials have been incorporated into films for use as barrier layers to enclose corrosion-susceptible items. In such embodiments, vapor phase corrosion inhibitors are released from the barrier film to engage with the enclosed item so as to protect the item from corrosion.
In other embodiments of the prior art, volatile corrosion inhibitor materials have been incorporated with a substrate to form a corrosion inhibiting product that may be placed adjacent to corrosion-susceptible items. A wide variety of substrates in a wide variety of configurations are useful in releasably containing the volatile corrosion inhibitor materials, with such substrates being fabricated from, for example, non-woven fabrics, paper, polymeric films, and foam materials, such as open cell urethane foams. In certain applications, adhesives may be applied to a surface of the substrate, such that the corrosion inhibiting product may be adhesively affixed to a location adjacent to the targeted corrosion-susceptible items.
It has been found that such corrosion inhibiting products may be disposed within a permeable enclosure that allows the vapor phase corrosion inhibitor to be emitted out from within the enclosure to protect adjacent corrosion-susceptible items. An example permeable enclosure for volatile corrosion inhibitor materials is described in U.S. Pat. No. 5,422,187, which is incorporated herein by reference. The permeable enclosure barrier described in U.S. Pat. No. 5,422,187 allows vapors to pass therethrough but prevents emission of solid particles out from the enclosure.
A particular application for corrosion inhibitor products contained within a gas-permeable enclosure is in the fabrication of semiconductors and related electronic components. Such components are typically manufactured in “clean room” environments so as to prevent contamination during the manufacturing process. In addition to attempting to prevent particle contamination of such electronic components, manufacturers have also taken steps to minimize exposure to moisture and other airborne chemical contaminates, which can partially corrode delicate metal elements in the electronic devices. One measure commonly taken is to limit the time of exposure to the clean room environment between processing steps which expose metal surfaces of the electronic device. These queue times in conjunction with ambient moisture controls are used to successfully process semiconductor devices without incurring corrosion of metallic features.
It has been found that volatile corrosion inhibitor products can assist in preventing corrosion damage to such electronic components by placing the corrosion inhibiting products in proximity to the electronic components to thereby expose such components to vapor phase corrosion inhibitors. To eliminate the risk of particle contamination of the electronic components, from, for example, degradation of the corrosion inhibitor product or emission of solid volatile corrosion inhibitors, the corrosion inhibitor products are preferably enclosed within a gas-permeable, solid particle-impermeable barrier.
In researching the effectiveness of currently available gas-permeable barrier enclosed corrosion inhibitor products, Applicants have determined that a relatively high concentration of vapor phase corrosion inhibitors present in a treatment zone is desired for insuring corrosion protection of the electronic components stored therein. However, due to the volatile nature of the corrosion inhibitor materials in the corrosion inhibitor products, the effectiveness of such corrosion inhibitor products decreases over time when exposed to ambient conditions as a result of vapor pressure equilibration effects. In the course of experimentation and testing, it has now been discovered that corrosion inhibitor products disposed in gas-permeable barriers alone have the tendency to lose effectiveness over time.
In addition, it has been found that the release rate of vapor phase corrosion inhibitors from the corrosion inhibiting products is limited by the total surface area of the supporting substrate that is capable of emitting vapor phase corrosion inhibitors to the ambient surroundings.
Accordingly, it is a principal object of the present invention to provide a volatile corrosion inhibitor package that incorporates a gas-impermeable outer enclosure barrier that maintains a desired elevated corrosion inhibitor vapor pressure adjacent to the corrosion inhibitor product.
It is a further object of the present invention to provide a volatile corrosion inhibitor package that incorporates an outer gas-impermeable barrier layer and a gas-permeable, solid particle-impermeable inner barrier layer within which a corrosion inhibitor product is disposed until it is ready for use.
It is a still further object of the present invention to provide a corrosion inhibitor product having an enhanced emission surface area for accelerating release of vapor